This invention relates to a system for integrally controlling an automatic transmission and an engine, and more particularly to improvements in a system for integrally controlling an automatic transmission and an engine, wherein the engine torque is temporarily changed by a predetermined value during shifting to maintain satisfactory shift characteristics.
Automatic transmissions comprising gear transmission mechanisms, a plurality of frictionally engaging devices, and hydraulic pressure control devices operated to selectively switch the engagements of the frictionally engaging devices, so that any one of a plurality of gear stages can be achieved in accordance with a present shift map, are well known in the transmission art.
Furthermore, an automatic transmission has heretofore been widely known, wherein two types of shifting patterns are performed in accordance with the aforesaid shift maps: a power pattern (power performance mode) and an economy pattern (fuel consumption performance mode). Running characteristics in compliance with the intention of a driver can be selected.
Furthermore, in an automatic transmission for a vehicle of the type described, various systems have been implemented for integrally controlling an automatic transmission and an engine, wherein engine torque is changed during shifting to obtain satisfactory shift characteristics and durability of the frictionally engaging devices (For example, Japanese Patent Laid-Open No. 69738/1980). More specifically, in such systems the amount of torque transmitted from the engine is changed during shifting and the amount of absorbed energy in various members in the automatic transmission or in the frictionally engaging devices for controlling these members is controlled so as to complete shifting within a short period of time under a low shift shock.
In the above-described system for integrally controlling an automatic transmission and an engine, normally, a change value of engine torque is determined by engine load (throttle opening, for example) and the type of shifting.
However, in the above-described automatic transmission wherein the shift patterns can be selected, even under the same engine load and the same type of shifting, engine rotary speeds during shifting differ with respective shift patterns. As a consequence, the amount of energy absorbed by the frictionally engaging devices differs with respective shift patterns. The torque change value in the automatic transmission has heretofore been determined on the basis of the power pattern in order to secure the durability thereof. Because of this, even if the economy shift pattern is selected (which pattern does not require as high a torque change value), the same torque change as during power shift pattern selection has been performed. As a result, such disadvantages as increased shift shock due to shortened shift time durations and unnecessary increases in temperature in the exhaust system arise.